In the field of mobile devices, such as cellular telephone and Blackberrys, a small form factor is an increasingly important design consideration. Such devices typically include battery packs having power lines and input/output lines. In some instances, however, the small form factor of battery packs makes it difficult to provide sufficient pins for communicating.
Accordingly, it is known to provide a combined power and input/output pin or pins on an integrated circuit or other device. Such solutions typically include a diode and capacitor or a resistor and capacitor to extract power and store it for the device.
The diode-capacitor solution, however, has proven to be disadvantageous in low voltage systems. More particularly, in such systems, the diode drop may be insurmountable.
The resistor-capacitor solution is disadvantageous owing to baud rate and power consumption contention. That is, low power consumption requires large resistors which require longer on-times and lower baud rates which increase power consumption.
Furthermore, in very low voltage combined power and communications applications, there may not be sufficient Vdd to allow other operations, such as self-writing the flash memory.
As such, there is a need for an improved combined low power and input/output solution that allows for additional operations.